Piezoelectric apparatus



Dec.1s,1941; Y. O WHES- 2,266,381

' PIEZELECTRIC APPARATUS Filed Jan. 26, 19:58 '2 sheets-sheet 1 WMM NTOR. OMG/dawg ATTORNEYS Dec. H6, 19411. o, w- P155 2,266,381

PIEZOELECTRIC APPARATUS Filed Jan. 26, 1938 2 Sheets-Sheet 2 Ill I BY Z MNTOR.

Www/WM5 ATTORNEYS I 1 Patented Deeii, 1941 UNTE@ STATES PATENT @EFQE accessi rmzosmncrarc arrana'rps @thmar W. lPies, Cincinnati, @his amusante mamey 2e, rese, semina. reacts (ci. iti-352) l@ Claims.

crystals such as Rochelle salt, quartz, and Atourmaline, which is known as piezo-electric eiect. In this apparatus, in principle, the mechanical force due to the incidence of a sound wave maniiests itself as an electrical charge upon opposite faces of a crystal cut in a specied manner. Conversely, impressions of electrical wave cur rents, as of a train of speech, upon the opposite .the phenomena exhibited by certain salts and faces of the crystal, cause corresponding mechanical vibrations to be set up therein. The piezo electric eirect thus may be used either to convert electrical translating energy into mechanical form, or mechanically translating energy into electrical impulses. Y

Ingeneral, the piezo electric eiect and means for utilizing the phenomena are old and well known. However, the present invention resides in improvements through which better advantage o the phenomena may be obtained.

The typical piezo apparatus comprises, usually, a pair of plates or crystals of Rochelle salt placed adjacent one another, with one charge collecting means constituting an electrode located between the plates and other charge collecting means constituting the other electrode located on the outer surfaces of the respective crystals. For protection the structure usually is coated with wax or paint. In the remainder of the speciiication, as in the art, this combination of y.elements is termed the "piezo crysta The present invention is directed, particularly,

to means for mounting this crystal in such a7 manner that it may receive feeble mechanical vibrations or feeble sound impulses of variable character and translate 4them accurately and eiciently to corresponding electrical charges, in the manner of a microphone, or, conversely, to a combination in which the crystal is mounted faithfully to translate electrical energy impressed upon it to mechanical movement, for reproduction of the electrical vibrations into sound waves, as in sound speaker apparatus.

Briey, the apparatus of the invention comacterlzed in that it is suited specifically for use.,

prises, the piezo crystal, an expansible frame,

and means-connecting the crystal with the frame to warp the crystal when the frame is expanded. The frame is conflgurated or constructed to receive directional impulses and expand or distort in order to revolve these into relative opposing movements at opposing points of connection for application to the crystal.

Otherwise expressed, the invention contemplates a frame which expands and contracts in one direction when subjected respectively tacompression or extension in another direction. The expanding and contracting movements, or the forces which they represent, in turn, are compounded-upon the piezo crystal, itself, through connecting means, whereby the crystal is placed within a state of warp or distortion, the degree of which corresponds to the magnitudel of the directional forces applied to the frame. Under such conditions, the crystal generates the piezoelectrical impulse corresponding to the mechanical movements, or vibrations, to which the microphone was subjected with high fidelity of reproduction. The piezo-electrical impulses, in turn, are amplied for audibility.

If the apparatus be used in a speaker system, the mechanical movements, manifested by the crystal through impression of electrical currents thereon, are transferred through the connecting means to the frame, wherein they are resolved and unified to directional mechanical movements suited for the operation of -a speaker diaphragm or the like. L

As an illustration, a typical embodiment of the invention comprises a distortable frame made up of elements forming a yieldable rhomboid figure adapted to receive and mount the crystal. Directional movements or vibrations applied at an apex of the rhomboid cause movements of opposing direction at the adjacent apices. The magnitude' of thesemovements is greater, less, or equal, depending upon the geometry of the frame figure to the movements at the apex points at which the initiating movement was applied. Links connecting the opposite apices with alternate respective sections of the crystal place the crystal within a state of compound warp.

From the brief foregoing description, the aptitude of the device for use either as a piezo microphone or as a piezo speaker will be understood by those who are skilled in the art, and, for this reason, the preferred embodiment of' the invention is disclosed only in the form of microphone apparatus. However, this structure also is charln work in which the vibrations and sound are notably feeble and complex, as in water leak detection.

The preferred embodiment of the invention is disclosed in the accompanying drawings in which:

Figure 1 is a perspective View of a microphone apparatus of the invention with the housing and supporting parts shown in assembled relation.

Figure 2 is a sectional elevation taken on a line longitudinal through the apparatus, showing the face view of the piezo crystal.

Figure 3 is a detailed elevation, similar to Figure 2, but with the apparatus turned to 90.

Figure 4 is a cross sectional view taken on the line 4--4 of Figure 3.

Figure 5 is a diagrammatic view illustrating compounding of the movement of the frame upon the crystal as the frame is moved or vibrated.

Figure 6 is a perspective view of the assembly of the apparatus with the cover and inertia weight removed.

In the drawings, the piezo crystal is indicated generally at l. This crystal comprises lplates of sodium potassium tartrate 2, 2, placed adiacent one another, but separated by a foil electrode 3. Pieces of foil 4, 4 are placed on each of the outer faces of the plates of crystal and are joined together, as at 5, to constitute the other electrode of the piezo crystal system. The electrodes 3 and 5 are connected respectively to the terminals of a lead 6, which carries a plug-in jack I to facilitate electrical connection of the microphone apparatus with amplification apparatus, as shown in Figure 6.

The piezo crystal is sustained in a frame indicated generally at 8. 'I'his frame, in the preferred embodiment of the invention comprises a plurality of flexible limbs or arms 9 constituting a generally rhomboidal geometric gure. The limbs of the preferred structure are of V-shape and are oppositely arranged in a plane and interconnected so as to provide a frame which is distortable in shape in the plane of its configuration. Each of the arms 9 preferably is tapered toward its terminal portions, so that the junctures Il), I of adjacent arms are relatively flexible in relation to the arm elements thus stiffened. The frame preferably is made from a single piece of metal, as by stamping or shaping, so that the arms or limbs are integral with one another. Both the lower and upper ends of the frame terminate in pivot portions II, I2, respectively, the one engaging a pedestal support'indicated generally at I3, and the other carrying a weight element I4, the function of which is explained at a later point in the specification. From this de- I scription it will be seen that the frame can be distorted in shape by pressure applied in the plane of the frame at a pair of oppositely disposed points upon it to produce a movement in said plane in opposite directions at another pair of oppositely disposed points ofthe frame.

Alternate or opposing corner portions of the piezo crystal are connected respectively tothe frame at juncture points I0, I0, through'beam and hanger assemblies I and I6, located on opposite sides of the crystal member. sembly, the piezo crystal is carried within the frame, with the plane of the crystal being lateral or at right angles to the plane of the frame. Each beam and hanger assembly comprises a pair of corner hangers I'I, II, the respective hangers of one pair being disposed over opposing alternate corners lof the crystal to face one side of the In the asframe, and the hangersof the other pair being disposed respectively over the remaining alternate corners of the crystal to face the other side of the frame. The beam or yoke members of the assemblies pass through the respective hangers of the pairs and are tied to the juncture points I0, I0 by means of draw bolts I9, I9 which pass through bores in the frame, appropriately provided, to carry draw nuts 20, 20. In this manner,

' two opposing corners of the crystal are tied to one point of the frame, two other opposing corners of.

the crystal are tied to an opposing point of the frame and relative movements of the tie points on the frame cause compound distortion of the crystal held therebetween.

The lower pivot portion I I of the frame is fitted to a bore in a pedestal cap 2I which, in turn, also is bored to engage a stud 22 extending from the pedestal I3. The pedestal cap piece is flanged at the upper portion to receive and hold a rubber mounting ring 24. The pedestal I3 comprisestripod legs 25 fixed to a hub piece 26. From the drawings it may be seen that the frame cap piece and pedestal all are in resting mechanical position. Vibratory movements of the tripod, or the surface upon which it rests, are carried upwardly through the frame in which they are manifested as mechanical movements of opposing direction at the junctures I0, Il.

The upper pivot I2 of the frame. is threaded to carry an inertia weight 21, as shown in Figure 3. This weight is provided with a clearance bore 23, within which the arm portions of the frame are disposed to compact the structure. The inertia weight 2'I also is provided with a stud portion 23 which is adapted to carry a rubber mounting ring 29, similar to the rubber ring 24.

A cylindrical housing 30 is carried upon the upper mounting ring 23 in resting relationship, while a lower housing member 3|, turned to telescopically engage the upper housing member, is held in position with the bottom in abutment with the lower mounting ring 24. The housing is provided with abore 32, carrying a grommet 33, through which the lead line i is passed. A bracket 34 is carried upon the upper surface of the flange of the pedestal cap in order to hold the lead line in position within the microphone housing.

'Ihe function of the combination of elements is illustrated diagrammatically in Figure 5. From the foregoing description it will be seen that the frame is relatively extensible or expansible. If one point of the frame be held stationary or relatively so, as the point 35 of Figure 5 which corresponds to the inertia weight of the apparatus, and if a force or vibratory movement 31 be applied at the lower point of the frame corresponding to the lower pivot II of the structure, then the frame longitudinally will tend to be compressed. This compressing movement, however, is accompanied only with a corresponding expanding movement of the frame, of lateral direction, at the juncture points. Upon longitudinal compression, therefore, the points I0, III move outwardly in opposing directions as indicated by the arrows 33 and 39. Two opposing corners of the piezo crystal, which are tied to the one juncture point through the hangers and beam, thus will be warped toward the direction of the arrow 38, while the two other corners of the crystal, tied to the other juncture point I0, will be warped in the direction of the arrow 39, placing the crystal within a state of compound warpage, which is continued during manifestation of the particular movement in the direction of the parts when the frame is compressed axially.

I 2,266,381 arrow as. since the-crystal is elastic to a limited frame and of the crystal. The oppositely disposeds flexible limbs of the frame are in interconnection at their terminal portions and diverge in response to axial pressure upon the frame, while the crystal is disposedbetween the limbs and two opposite points upon it are yokedto one of the limbs and another pair of relatively opposite points is yoked to the other of the limbs, so that the crystal is warped in compound directions for generation of electricity proportional to the extent vof the warpage.

It will be understood, of course, that all of these movements are of a very low order of magnitude and rarely, if ever, will approach as much as one-thousandth of an inch, being more likely inthe order of one hundred-thousandth or one ten-thousandth of an inch. understood that the reversal of direction in a typical vibratory motion occurs at highly frequent intervals. For instance, the frequency of vibration induced by a typical water leak will be in the order of, perhaps, three to six hundred cycles per second.

The function of the inertia weight is to provide, within the apparatus, a point, relatively iixed and stationary, to permit relative movement of the arm parts of the frame with one another. Thus, the inertia of the weight is greater than that of the arm structure of the frame and the crystal mounting structure, and the yieldable juncture points of the frame thus are permitted to move while the upper part 35 remains iixed.

The inertia weight has another function. By adjustment in the mass of the weight, I have determined that it is possible to adjust the natural frequency to which the microphone is responsive. As the size of the weight is increased, the natural frequency of response of the microphone decreases. Thus, if sounds of a very high frequency or pitch are intended to be received or detected, then it may be appropriate only to use a very light weight or none at all. In place of the inertia weight, an ladjustable or xed spring or a cup containing lead balls may be used.

While the compounding function of the frame of the invention is illustrated most easily in relation to a rhomboid or equilateral, geometric coniiguration, it will be understood that other configurations for the frame may be used. For instance, in place of the diamond shaped connguration, a circular frame or a yoke shaped frame in which each of the arms is urged against vertical movement, may be provided;

Prior to the normal course of usage of the apparatus, the draw nuts 2li, 2li are tightened untilv the crystal is positioned securely within the mounting, with the hanger parts andthe beams in slightly tensioned relationship against the frame.

The perspective view of the assembly of parts, as shown in -jFigure 6, illustrates the manner in which the crystal is supported from the, hangers and the hangers. in turn. are supported from theA frame so that when the points of Support upon the frame are moved in opposite directions, the hangers effect the compound warping of the crystal. Thus the arrows shown on the gure indicate the relative direction of movement of the Likewise, it will be of the crystal to one of the limbs` o f the frame,-

The microphone apparatus of the invention may be used for detecting water leak sounds; for example, 'simply by standing the apparatus on its tripod upon the surface ofthe street below which the suspected leaky `main may be located, the vibrations carried through the intervening layer of earth are sumcient for registration upon the microphone. Alternately, a iitting, which is not illustrated, may be used in place of the tripod, to carry the microphone apparatus directly upon the valve stem of a re hydrant. In this case, of course, the vibrations are-of a larger magnitude.

Preferably, all of the parts are made of aluminum, Monel metal, or stainless steel to resist corrosion from the atmosphere.

If the improvements of the invention be used to provide piezo speaker apparatus, as distinguished from piezo microphone apparatus, it will be understood that the same principle of operation is applicable. In this case, warping and distortion of the lcrystal induced by the impression of electrical currents upon the crystal, is transferred through the-connecting assembly into opposing movements, for instance at the juncture point `of the frame which is thus extended or contracted for mechanical movement at the lower pivot point to which the speaker diaphragm may be connected. In such speaker apparatus it is preferable to have stiff link connections between the relatively opposed corners of the crystal and the respective points of the frame. The apparatus thus may be used in horizontal as well as vertical position.

lHaving described my invention, I claim:

1. A piezo electric unit, comprising, a. piezo crystal, a frame comprised of oppositely disposed flexible limbs arranged in a plane, said limbs being interconnected in such manner that the frame is distortable in the plane of its configuration, so that it can be distorted in shape by pressure applied in said plane at a pair of oppositely disposed points upon the frame to produce movement in said plane in opposite directions at another pair of oppositely disposed points on saidframe, with the frame surrounding the crystal, yoke means interconnecting two oppositely disposed portions and other yoke means connecting two other relatively oppositely disposed portions of the crystal to the other limb of the frame, whereby the crystal is warped in compound directions when the yoke means are moved in relatively opposite directions.

2. A piezo electric unit, comprising, a frame which is constructed of oppositely disposed flexible limbs, said frame being distortable in the plane of its configuration, so that it can be distorted in shape by pressure applied to the frame in said plane at a pair of oppositely disposed points on the limbs, to produce movement in said plane in opposite directions at another pair of oppositely disposed points on the limbs, a piezo crystal disposed Within the frame, a hanger interconnecting two relatively oppositely disposed portions of said crystal to one of the limbs, and another hanger connecting two other relatively oppositely disposed portions of the crystal to the other of the limbs, whereby the crystal is warped 'in compound directions when the hangers are moved relatively away from one another.

v 3. A piezo electric unit, comprising, a vibratory frame constructed of oppositely disposed substantially v-shaped limbs arranged to form a frame,\said frame being distortable in the plane of its configuration, so that pressure applied upon the frame in said plane at the correspondingr apices of the said limbs distorts the frame to produce movement in said plane in opposite directions at the two oppositely disposed mid sections of the limbs, yoke means interconnecting two relatively oppositely disposed portions of the crystal to the mid section of one of the limbs and other yoke means connecting two other relatively oppositely disposed portions of the crystal to the mid section of the other limb, whereby the crystal is subjected to compound warping so as to generate piezo electricity when pressure is applied in the plane of the frame upon the said apices thereof. A,

4. A microphone comprising a frame which is distortable in the plane of its conguration, means for applying vibratory motion to the frame in its plane of distortion, hangers respectively 'connected to oppositely disposed points upon the frame and extending generally toward one another within it, and a piezo crystal having two oppositely disposed points supported by one of the hangers and two other oppositely disposed points supported by the other of the hangers, whereby, when the oppositely disposed points upon the frame are moved, in response to the application of vibratory motion applied to the frame through said means, the crystal is warped in compound directions through said hangers.

5. A microphone'comprising a base, an inertia member, a iiexible frame intermediate the base and the inertia member, said frame being distortable in the plane of its conguration, two points of the frame being adapted to be moved away from one another when ,the base and the inertia vmember are moved toward one another, hangers supported from said two oppositely disposed points upon the frame intermediate the base and' the inertia member, the hangers residing in intersecting planes relative to one another and relative to the plane of the frame, and a crystal having two oppositely disposed points supported from one of the hangers and two other oppositely disposed points supported from the other of the hangers.

6. An assembly comprising a pair of hangers facingone another in spaced relationship but with the one hanger residing in a plane approximately 90 degrees removed from the plane of the other, the hangers having terminal portions extending in opposite directions, a flexible frame disposed in a plane intersecting the planes of both of said hangers and supporting the terminal portions of the hangers from points upon the frame which move in opposite directions when the frame is compressed, the said hangers including means adapted to carry a. piezo crystal therebetween, whereby the piezo crystal is warped in compound directions whenthe frame is axially compressed.

7. An apparatus of the type described, comprising a pair of hangers which face one another but reside in intersecting planes, means carried by one of the hangers for supporting two oppositevly disposed corner portions of a piezo crystal, and

aaceei rections, and a frame for supporting the oppositey ly extendingterminal portions of the hangers whereby the hangers are adapted to warp the crystal in compound directions when the terminal portions of the hangers are moved away from one another. j

8. An assembly comprising a substantially diamond-shaped frame, a hanger supported within the frame from one of the apices and residing in a plane intersecting the plane of the frame, another hanger supported within the frame from an opposite apex of it and residing in another plane intersecting the plane of the frame and the plane of the other hanger, and means carried by the hangers for supporting therebetween a piezo crystal in such manner that the piezo crystal is warped in compound directions when the said apices of the frame are moved in opposite directions.

9. An apparatus of the type described comprising a frame which is distortable in shape in the plane of its conguration in such manner that the said frame can be distorted in shape by pressure applied in said plane at a pair of oppositely disposed points of the frame, to produce movement in said plane in opposite directions at another pair of oppositely disposed points of the frame, hangers extending within the frame from two oppositely disposed points upon said frame and residing in intersecting planes, yoke means carried by one of the hangers and having apertures respectively adapted to embrace oppositely disposed corner portions of a piezo crystal positioned between the hangers, and yoke means carried by the otherof the hangers and having apertures respectivelyadapted to embrace other oppositely disposed corner portions of the piezo crystal.

l0. An assembly for warping a piezo crystal in response to vibrations, comprising a frame which is distortable in shape in the plane of its configuration in such manner that the said frame can be distorted in shape by pressure applied in said plane at a pair of oppositely disposed points of the frame, to produce movement in said plane in opposite directions at another pair of oppositely disposed points of the frame, yoke means carried by the frame from one of the points of the second mentioned pair of oppositely disposed points and adapted to be connected to two oppositely disposed portions of a piezo crystal, other yoke means carried by the frame from the other of the points of the second mentioned oppositely disposed pair and adapted to be connected to two other relatively oppositely disposed portions of the piezo crystal, and means forv supporting the frame in such manner that when the first mentioned points of support of the frame are moved in opposite directions, a piezo crystal carried by said yoke means is warped in compound directions.

OTHMAR W. PIES. 

